7. Giant Worlds and Satellites

Joshua Barnes -- Fall 1999

The outer Solar System contains two `failed stars' and two planets which are merely enormous by terrestrial standards. Jupiter & Saturn both radiate about twice as much energy as they receive from the Sun; this outflowing energy powers dramatic activity in these planets' magnetized interiors and atmospheres. Uranus & Neptune, though each about 15 times the Earth's mass, are less active. All these giants have systems of satellite and rings shaped by subtle dynamical effects over trillions of orbits, and possibly by collisions as well.

Topics:

• Gas giants & Water worlds
• Pressure balance
• Magnetic fields
• Satellite systems
• Tides & heating
• Planetary rings
• Resonances

Web Resources:

• Giant planets: Jupiter [source], Saturn [source], Uranus [source], Neptune [source].

  Portraits of the giant planets. Jupiter & Saturn are the two largest planets in the Solar System; in composition and structure they are inbetween planets and stars. Uranus & Neptune are smaller worlds with rocky cores and mantles of water & ice.

• Neptune Rotation (0.5 Mbyte mpeg) [source]

  Combining images from several sources, this movie shows storm-like features in Neptune's atmosphere passing as the planet spins about its axis.

• Satellites of Jupiter: Io [source], Europa [source], Ganymede [source], Callisto [source].

  The four satellites discovered by Galileo [source]. Callisto has an ancient, heavily cratered surface. The other three show evidence of past and present activity; Ganymede has plate-like features, Europa a frozen ocean which swiftly fills in impact craters, and Io is the most volcanic object in the Solar System!

• Satellites of Saturn: Enceladus [source], Titan [source].

  Enceladus, a fairly small satellite, nonetheless has diverse terrain indicating recent activity. Titan, the largest satellite of Saturn, is shrouded in thick clouds; these images were made using infrared light.

• Satellites of Uranus: Miranda [source], Ariel [source], Umbriel [source], Titania [source], Oberon [source].

  The satellites of Uranus are rather small and dark. Oberon, Titania, & Umbriel have ancient cratered surfaces, while Ariel & Miranda show signs of activity after the heavy bombardment ended.

• Satellites of Neptune: Triton [source]

  Triton has smooth plains as well as `cantaloupe terrain'; these were probably produced by the slow flowing of gas-rich ices.

• Saturn's Rings: Backlit view [source], Ring material [source], Details of rings [source].

  The rings of Saturn are bright lumps of ice orbiting the planet. Subtle gravitational effects have arranged the material into thousands of `ringlets'.

• Uranus: satellites & rings [source]

  This pair of Space Telescope pictures of Uranus show its rings and some of its many satellites. The rotation of the planet and the orbital motions of the satellites are visible.

• Ring formation (1.75 Mbyte mpeg)

  Computer simulation showing how the tidal disruption of a small satellite can lead to the formation of a ring.

Homework 7: Satellites of Jupiter, due 10/11.

Quiz 7: Alike & Different